Start on a new reference implementation

So far this includes the type-level schema validation and normalization logic. No domain-level validation is in place yet (i.e. checks on the contents of the strings involved; see #63).

.editorconfig

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+root = true
+
+[*]
+end_of_line = lf
+insert_final_newline = true
+charset = utf-8
+indent_size = 2
+indent_style = space
+trim_trailing_whitespace = true

.gitignore

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+/reference-implementation/node_modules/

.travis.yml

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+language: node_js
+node_js:
+  - stable
+
+before_install:
+  - cd reference-implementation
+script:
+  - npm run lint
+  - npm test
+
+branches:
+  only:
+    - master
+
+notifications:
+  email:
+    on_success: never
+    on_failure: always

reference-implementation/.eslintrc.yml

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+---
+root: true
+env:
+  es6: true
+  node: true
+parserOptions:
+  ecmaVersion: 2018
+
+rules:
+  # Possible errors
+  for-direction: error
+  getter-return: error
+  no-await-in-loop: error
+  no-compare-neg-zero: error
+  no-cond-assign: [error, except-parens]
+  no-console: off
+  no-constant-condition: [error, checkLoops: false]
+  no-control-regex: error
+  no-debugger: error
+  no-dupe-args: error
+  no-dupe-keys: error
+  no-duplicate-case: error
+  no-empty: error
+  no-empty-character-class: error
+  no-ex-assign: error
+  no-extra-boolean-cast: error
+  no-extra-parens: [error, all, { conditionalAssign: false, nestedBinaryExpressions: false, returnAssign: false }]
+  no-extra-semi: error
+  no-func-assign: error
+  no-inner-declarations: off
+  no-invalid-regexp: error
+  no-irregular-whitespace: error
+  no-obj-calls: error
+  no-prototype-builtins: error
+  no-regex-spaces: error
+  no-sparse-arrays: error
+  no-template-curly-in-string: error
+  no-unexpected-multiline: error
+  no-unreachable: error
+  no-unsafe-finally: off
+  no-unsafe-negation: error
+  use-isnan: error
+  valid-jsdoc: off
+  valid-typeof: error
+
+  # Best practices
+  accessor-pairs: error
+  array-callback-return: error
+  block-scoped-var: off
+  class-methods-use-this: off
+  complexity: off
+  consistent-return: error
+  curly: [error, all]
+  default-case: off
+  dot-location: [error, property]
+  dot-notation: error
+  eqeqeq: error
+  guard-for-in: off
+  no-alert: error
+  no-caller: error
+  no-case-declarations: error
+  no-div-regex: off
+  no-else-return: error
+  no-empty-function: off
+  no-empty-pattern: error
+  no-eq-null: error
+  no-eval: error
+  no-extend-native: error
+  no-extra-bind: error
+  no-extra-label: error
+  no-fallthrough: error
+  no-floating-decimal: error
+  no-global-assign: error
+  no-implicit-coercion: error
+  no-implicit-globals: off # Userscripts run in their own scope
+  no-implied-eval: error
+  no-invalid-this: error
+  no-iterator: error
+  no-labels: [error, allowLoop: true]
+  no-lone-blocks: error
+  no-loop-func: error
+  no-magic-numbers: [error, { ignore: [0, 1] }]
+  no-multi-spaces: error
+  no-multi-str: error
+  no-new: error
+  no-new-func: error
+  no-new-wrappers: error
+  no-octal: error
+  no-octal-escape: error
+  no-param-reassign: off
+  no-process-env: error
+  no-proto: error
+  no-redeclare: error
+  no-restricted-properties: off
+  no-return-assign: [error, except-parens]
+  no-return-await: error
+  no-script-url: off
+  no-self-assign: error
+  no-self-compare: error
+  no-sequences: error
+  no-throw-literal: error
+  no-unmodified-loop-condition: error
+  no-unused-expressions: error
+  no-unused-labels: error
+  no-useless-call: error
+  no-useless-concat: error
+  no-useless-escape: error
+  no-useless-return: error
+  no-void: error
+  no-warning-comments: off
+  no-with: error
+  prefer-promise-reject-errors: error
+  radix: [error, as-needed]
+  require-await: error
+  vars-on-top: off
+  wrap-iife: [error, outside]
+  yoda: [error, never]
+
+  # Strict Mode
+  strict: [error, global]
+
+  # Variables
+  init-declarations: off
+  no-catch-shadow: error
+  no-delete-var: error
+  no-label-var: error
+  no-restricted-globals: off
+  no-shadow: error
+  no-shadow-restricted-names: error
+  no-undef: error
+  no-undef-init: error
+  no-undefined: off
+  no-unused-vars: error
+  no-use-before-define: [error, nofunc]
+
+  # Node.js and CommonJS
+  callback-return: off
+  global-require: error
+  handle-callback-err: error
+  no-buffer-constructor: error
+  no-mixed-requires: [error, true]
+  no-new-require: error
+  no-path-concat: error
+  no-process-exit: error
+  no-restricted-modules: off
+  no-sync: off
+
+  # Stylistic Issues
+  array-bracket-newline: [error, multiline: true]
+  array-bracket-spacing: [error, never]
+  array-element-newline: off
+  block-spacing: [error, always]
+  brace-style: [error, 1tbs, allowSingleLine: false]
+  camelcase: [error, properties: always]
+  capitalized-comments: off
+  comma-dangle: [error, never]
+  comma-spacing: [error, { before: false, after: true }]
+  comma-style: [error, last]
+  computed-property-spacing: [error, never]
+  consistent-this: off
+  eol-last: error
+  func-call-spacing: [error, never]
+  func-name-matching: error
+  func-names: off
+  func-style: [error, declaration]
+  function-paren-newline: [error, multiline]
+  id-blacklist: off
+  id-length: off
+  id-match: off
+  indent:
+  - error
+  - 2
+  - SwitchCase: 1
+    CallExpression:
+      arguments: first
+    FunctionExpression:
+      parameters: first
+    ignoredNodes:
+    - ConditionalExpression
+  jsx-quotes: off
+  key-spacing: [error, { beforeColon: false, afterColon: true, mode: strict }]
+  keyword-spacing: [error, { before: true, after: true }]
+  line-comment-position: off
+  linebreak-style: [error, unix]
+  lines-around-comment: off
+  max-depth: off
+  max-len: [error, 120, { ignoreUrls: true }]
+  max-lines: off
+  max-nested-callbacks: off
+  max-params: off
+  max-statements: off
+  max-statements-per-line: [error, max: 1]
+  multiline-ternary: [error, always-multiline]
+  new-cap: error
+  new-parens: error
+  newline-per-chained-call: off
+  no-array-constructor: error
+  no-bitwise: off
+  no-continue: off
+  no-inline-comments: off
+  no-lonely-if: error
+  no-mixed-operators:
+    - error
+    - groups:
+      - - "&"
+        - "|"
+        - "^"
+        - "~"
+        - "<<"
+        - ">>"
+        - ">>>"
+      - - "=="
+        - "!="
+        - "==="
+        - "!=="
+        - ">"
+        - ">="
+        - "<"
+        - "<="
+      - - "&&"
+        - "||"
+      - - in
+        - instanceof
+  no-mixed-spaces-and-tabs: error
+  no-multi-assign: off
+  no-multiple-empty-lines: error
+  no-negated-condition: off
+  no-nested-ternary: error
+  no-new-object: error
+  no-plusplus: off
+  no-restricted-syntax: off
+  no-tabs: error
+  no-ternary: off
+  no-trailing-spaces: error
+  no-underscore-dangle: off
+  no-unneeded-ternary: error
+  no-whitespace-before-property: error
+  nonblock-statement-body-position: error
+  object-curly-newline: [error, consistent: true]
+  object-curly-spacing: [error, always]
+  object-property-newline: off
+  one-var: [error, never]
+  one-var-declaration-per-line: [error, initializations]
+  operator-assignment: [error, always]
+  operator-linebreak: [error, after]
+  padded-blocks: [error, never]
+  padding-line-between-statements: off
+  quote-props: [error, as-needed]
+  quotes: [error, single, { allowTemplateLiterals: true }]
+  require-jsdoc: off
+  semi: [error, always]
+  semi-spacing: error
+  semi-style: error
+  sort-keys: off
+  sort-vars: off
+  space-before-blocks: [error, always]
+  space-before-function-paren: [error, { anonymous: always, named: never }]
+  space-in-parens: [error, never]
+  space-infix-ops: error
+  space-unary-ops: [error, { words: true, nonwords: false }]
+  spaced-comment: [error, always]
+  switch-colon-spacing: error
+  template-tag-spacing: error
+  unicode-bom: error
+  wrap-regex: off
+
+  # ECMAScript 6
+  arrow-body-style: off
+  arrow-parens: [error, as-needed]
+  arrow-spacing: error
+  constructor-super: error
+  generator-star-spacing: [error, after]
+  no-class-assign: error
+  no-confusing-arrow: off
+  no-const-assign: error
+  no-dupe-class-members: error
+  no-duplicate-imports: error
+  no-new-symbol: error
+  no-restricted-imports: off
+  no-this-before-super: error
+  no-useless-computed-key: error
+  no-useless-constructor: error
+  no-useless-rename: error
+  no-var: error
+  object-shorthand: error
+  prefer-arrow-callback: error
+  prefer-const: [error, ignoreReadBeforeAssign: true]
+  prefer-destructuring:
+  - error
+  - VariableDeclarator:
+      array: false
+      object: true
+    AssignmentExpression:
+      array: false
+      object: false
+  - enforceForRenamedProperties: false
+  prefer-numeric-literals: error
+  prefer-rest-params: error
+  prefer-spread: error
+  prefer-template: off
+  require-yield: error
+  rest-spread-spacing: error
+  sort-imports: off
+  symbol-description: error
+  template-curly-spacing: [error, never]
+  yield-star-spacing: [error, after]

reference-implementation/__tests__/.eslintrc.yml

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+---
+env:
+  jest: true